Combustion chamber and method of forming combustion chamber cavities



IN V EN TOR. 7/7m%/Z77072$ Dec. 23, 1958 M. H. FRANK COMBUSTION CHAMBER AND METHOD OF FORMING COMBUSTION CHAMBER CAVITIES Filed July 23, 1956 ATTOPNEK United States 1;:

COMBUSTION CHAMBER AND METHOD OF FORMING COMBUSTION CHAMBER CAVITIES Mark H. Frank, Birmingham, Mich.,assignor to Generai Motors Corporation, Detroit, Mich., a corporation of Delaware Application July 23, 1956, Serial No. 599,426 3 Claims. (Cl. 123-191) This invention relates to combustion chambers for engines, particularly internal combustion engines for automotive and other uses, and has particular relation to combustion chamber cavities in the heads of engines and to a method of manufacturing or finishing such cavities.

Combustion chamber cavities of the wedge type have been constructed by forming end surfaces and side surfaces in the heads of engines, the end surfaces being substantially plane surfaces disposed obliquely to the plane lower surfaces by which the heads are secured to the cylinders of the engine. If the end surfaces of the cavities intersect the plane surfaces of the heads it is possible to form or to machine such cavities by employing a rotating tool which may be moved laterally with respect to the axis of rotation with the end of the tool forming the obliquely disposed end surfaces of the cavities. if such end surfaces do not intersect the plane surfaces of the heads in which the cavities are formed then it is necessary to form the cavities by employing a rotating tool that is projected axially into the head in a direction normal to the plane end surfaces of the cavities and then moved laterally to form the side surfaces. In the event the cavities are formed by projecting the tool axially inwardly and then laterally it will be apparent that the side surfaces of the cavities either must be normal with respect to the end surfaces or be divergent with respect to the end surfaces. If the side surfaces are normal to the end surfaces and the inlet and exhaust valves are large it is difficult in high compression engines, where the cavities must be relatively small, to open the valves with-out tending to restrict the flow of fluid to and from the cavities. This tends to decrease the volumetric efficiency and the power of the engine. If the side surfaces of the cavities are divergent then the cavities tend to become wider than necessary and to overlap the ends of the cylinders thereby providing pockets where carbon and other deposits may be collected.

It is now proposed to construct wedge type ccmbustion chamber cavities in the heads of engines which have end surfaces that do not intersect the plane lower surfaces of the heads and which have side surfaces that are divergent and convergent from the end surfaces of the cavities toward the cylinders. To construct or finish such cavities it would ordinarily be necessary to project a finishing tool axially inwardly into the heads at a distance from the side surfaces, then move the tool to the side surfaces and around the cavity in a closed path. As it is proposed to form the cavities one of the foregcing steps is unnecessary. It is possible to project the tool into the head in engagement with one of the side surfaces, then move the tool in a closed path until the side surfaces are completely formed.

With the divergent and convergent side surfaces proposed the cavities provide ample clearance for opening and closing the valves, but do not become wide enough to form pockets outside the cylinders. Also as the cavities are formed it is possible to provide a venturi efiect on the opposite sides of the seats of both the inlet and exhaust valves. The clearance upon opening either the inlet and exhaust valves is such that the spaces between the valves and the seats gradually increase both inwardly and outwardly of the cylinders thereby providing for the flow of gas through the valves with the least possible loss.

In the drawing:

Figure l is a fragmentary cross sectional view of an internal combustion engine having combustion chamber cavities formed in the heads thereof, according to the principles of the invention.

Figure 2 is a fragmentary cross sectional view of one of the engine heads having a forming or finishing tcol applied thereto and illustrating how the cavities in the heads may be formed or finished.

Figure 3 is a fragmentary plane view of the lower surface of one of the engine heads and illustrates the path of movement of the tool employed .in forming or finishing one of the cavities.

The engine 10 in which the invention is embodied cornprises a cylinder block 11 having a cylinder 12 formed therein and in which a reciprocating piston 13 is employed. The cylinder 12 is one of a plurality of cylinders in which pistons 13 may be employed in the V-type engine for automotive and other purposes illustrated at Hi. The cylinders in the rows of cylinders in the block 11 may be closed at the ends by heads 14 secured to the block 11 by bolts indicated at 16. Each of the cylinders 12 is provided with a combustion chamber into which explosive charges are compressed by the pistons 13. The combustion chambers embody clearance spaces 17 between the pistons 13 and the plane lower surfaces 15 of the heads 14 and firing chambers or combustion chamber cavities 18 extending into the heads through the plane surfaces of the heads. The cavities 18 cornmunicate with the atmosphere through exhaust passages 15 which terminate at the cavities in exhaust ports 21. The cavities 18 also communicate with the induction system 26 for supplying explosive charges to the cylinders 12 of the engine through inlet passages 22 terminating at the cavities in inlet ports 23. The inlet ports 23 are adapted to be opened and closed by inlet and exhaust valves 24- and 26. The inlet and exhaust valves 24 and are adapted to be operated by any suitable valve actuating mechanism 27 operated by the camshaft of the engine in timed relation to the operation of the pistons 13. Each of the cavities 18 has a pocket 28 projecting therefrom in which the terminals 29 of a spark plug 31 are located. The spark plugs 31 are secured in threaded openings formed in the heads 14.

The cavities 18 are formed by plane end surfaces 32 through which the ports 21 and 23 for each cyiinder open. The plane end surfaces 32 are disposed obliquely to the plane lower surfaces 15 of the heads 14. The side surfaces of the cavities 18 are formed by divergent surfaces 33 extending from the plane surfaces 32 and by convergent surfaces 34 therebeyond. The divergent surfaces 33 extend entirely around the cavities 18, the convergent surfaces 34 intersect the plane lower surfaces 15 and do not extend entirely around the cavities 18. The line beyond which the convergent surfaces do not extend is indicated approximately at point X in Figure 2. The area of the plane surface 32 and the slope of the divergent surfaces 33 in each cavity 18 is such that the space available for opening the inlet and exhaust valves 24 and 26 increases from the ports 23 and 21, thereby increasing the size of the passages available for the flow of fluid between the valves and the ports. It will be apparent from examining Figure 1 that the space between the open valve and the divergent surface is considerably greater than between the open valve and the port. This provides venturi inlets and outlets through the inlet and exhaust ports, respectively. in Figure 1, for example, the explosive mixture flowing into the cavity 18 through: the, inletpassage ,22 will be compelled by the form of the passage 22 and the stem of the valve 24 to increase in velocitylas it approaches the'portZfa. Beyond the port23 the space available fo-rthe flow of fluid being greater, the -velocity ,of'the fluid will progressively decrease.

The pockets 28 for the spark plugs 33, communicating with each of the cavities 18, are formed throughout the extent of the divergent and convergent surfaces on one side of the cavities 18 and substantially midway between the inlet and exhaust valves of each cavity. The pockets are large enoughto enclose the spark plug terminals and to keepth e terminals out of the high velocity flow of fluid into the cylinders when the; inlet valves open. The turbulence involved in admitting combustibe mixture to the cylinders tends to collect'a reatively rich mixture in the pockets 28 to facilitate the firing of the charges under I all conditions of the operation of the engine.

The cavities 18 may be made or finished by employing a tool such as that indicated at The tool 36 has a plane end surface adapted to form the plane surfaces 32 when the tool rotates about the axis of the shaft 37. The tool also has divergent side surfaces with a slope identical to the slope of the divergent side surfaces 33 and convergent surfaces with a slope identical to the scope of the convergent surfaces 34. However, the tool 36 is not as wide as the cavities 18., The Width of the tool 36 is such that the line indicated at point X will not extend through the tool beyond a diameter of the tool. it will be apparcut that such a tool may be rotated and projected into one of the heads in the position indicated in dot and dash lines at 38 in Figure 3. Position 38 is any position where the center of rotation of tool 36 will be on the straight line indicated at 39. When projected into a head in this manner the tool then may be moved in a closed path in either direction along line 39, around semi-circular arcs 41 or 42 and throughout the extent of straight line 43. in the present instance it is considered preferable to form the cavities 18 so that each end of a cavity will be identical and the ends semi-cylindrical. However, this is not necessary as the cavities may be formed of any shape desired. Broken lines 44 and 46 illustrate the tool 36 in other positions in its path of movement in which the center of rotation of the tool follows the closed path indicated at 39, 41, 42, 43 or otherwise.

I claim:

1. A combustion chamber for engines comprising an engine head having a cavity formed in a plane surface thereof and adapted to communicate with a cylinder of an engine, said cavity being formed to include a substantially plane end surface disposed obliquely to said plane surface and side surfaces extending from said end surface and toward said cylinder, said side surfaces being formed to diverge away from said end surface and to converge beyond the diverging parts of said side surfaces, a pair of inlet and exhaust valves opening into said cavity through said end. surface, and means for opening and closing said valves within the diverging parts of said side surfaces, the slope of said diverging parts of said side sur faces being great enough to provide a greater valve opening between said valves andsaid diverging parts of said side surfacesthan between saidvalves and the seats forsaid valves.

2.-A combustion chamber for engines as defined by 1 claim 1 and in which said side surfaces intersect said plane surfaces of said head at one side of said cavity within said diverging parts of said side surfaces and at. the opposite side within said converging parts of said side surfaces.

3. A combustion chamber for engines as defined by claim 2 and in which said cavity is intersected by a spark-- plug pocket formed about an axis intersecting said cavity. on one side of and between said valves, said pocket beingv formed. to extend across the diverging and converging parts of said side surfaces at the side of said cavity having the greatest depth within said head, and a spark plug disposed in said head with the spark gap terminals thereof within said pocket, but beyond said surfaces of said cavity.

References Cited in the file of this patent UNITED STATES PATENTS 

